The present invention relates generally to a system and methods of machining hard tissues, such as bone, and more specifically to a system for the process and apparatus for laser assisted machining (“LAM”) of bone tissue.
Bone tissue is a type of dense connective tissue that is found in a variety complex internal and external structure. They are lightweight yet strong and hard to serve multiple functions. These rigid organs constitute part of the endoskeleton of vertebrates commonly known to protect the various soft organs of the body. In spite of their rigidity, bones are very active tissues that produce red and white blood cells and store minerals. Bones are made of a multiphase matrix of both organic minerals (i.e. collagen) and inorganic substances (i.e. hydroxyapatite). When bones are damaged, they usually heal quickly. However, in the case of a complicated breaks and deterioration due to (car) accidents and diseases (cancers) and the like, the damaged hard bone tissue must undergo replacement surgery, or bone graph.
One embodiment of the current invention can be used for machining bone tissue for surgical grafting. Bone grafting is a surgical procedure that replaces missing bone in order to repair extremely complex bone fractures, or to repairs that pose a significant health risk due to disease (cancer) to the patient. However, in order for bones to regenerate they require a very small fracture space or some type of scaffold to do so. Bone grafts may be autologous (bone harvested from the patient's own body, often from the iliac crest), allograft (cadaveric bone usually obtained from a bone bank), or synthetic (often made of hydroxyapatite or other naturally occurring and biocompatible substances) with similar mechanical properties to bone. Most bone grafts are expected to be reabsorbed and replaced as the natural bone heals over a few months' time.
The principals involved in successful bone grafts include osteoconduction (guiding the reparative growth of the natural bone), osteoinduction (encouraging undifferentiated cells to become active osteoblasts), and osteogenesis (living bone cells in the graft material contribute to bone remodeling), wherein it is understood that osteogenesis only occurs with autografts.
Another situation where bone tissue replacement and/or repair is necessary is total joint replacement such as knee, hip, shoulder, elbow, etc. Wherein often the entire damaged/diseased/malfunctioning bone tissues of the joint and partial bone tissues surrounding the joint are removed and replaced with an artificial inorganic (metallic/ceramic/polymeric) joint that is also grafted/integrated with the surrounding bone tissues.
The precision of particular surgical tools used for machining bone for the purpose of bone grafting and replacement is determined in part by the size and workspace of tools used. Conventional bone machining techniques include slicing, sawing, cutting, drilling, coring, milling, and grinding, with tools such as drills, saws, hammers, chisels, and grinders. These conventional techniques present significant limitations, such as high mechanical loading, high friction, and poor accuracy. Additionally, these conventional techniques are also slow, and usually cause damage to surrounding tissues, which may result in long recovery and healing times.
In contrast to conventional tool listed above, the minimum width of a laser beam is the width of a beam of light. As such, one advantages of doing surgeries using lasers instead of scalpel blades has resulted in less pain, less swelling and less bleeding for a majority of patients. As a laser beam can cut through tissues to seals blood vessels resulting in minimal bleeding. Lasers can also seal lymphatic vessels minimizing postoperative swelling, and it seals nerve ending reducing post-surgical pain. The fact that only the laser beam (not an instrument) touches the tissues (without any mechanical loading) eliminates much of the trauma that occurs using standard surgical techniques.
No successive laser technology has been reported to match a bone graft with the section of hard tissue (bone) that has been surgically removed due to disease/decay/damage. Moreover, the invention described herein can cut, drill, or shape the remaining healthy portion for integration with a bone graph or external biomaterial implant.
In order to effectively and efficiently machine a living bone work piece, without causing heat damage through overheating from mechanical loading and friction of the cutting tool, the present invention provides a novel system involving apparatus and process for laser-assisted bone machining that provides narrow beams with high power density, and creates little or no heat-affected zone (“HAZ”), thereby avoiding the difficulties experienced with conventional bone machining techniques.